[Pollution Characteristics of Carbonaceous Components in PM10 and PM2.5 of Road Dust Fall and Soil Dust in Xi'an].

To investigate the pollution characteristics of carbonaceous components in PM10 and PM2.5 of road dust fall and soil dust in Xi'an and enrich their source profiles, samples from five sites of road dust fall and 16 sites of soil dust were collected in Xi'an from April to May 2015. The ZDA-CY01 particulate matter resuspension sampler was used to obtain PM10 and PM2.5 samples, and the Model5L-NDIR OC and EC analyzer were used to determine the concentrations of organic carbon (OC) and elemental carbon (EC) in PM10 and PM2.5. The pollution and sources of carbonaceous aerosol in PM10 and PM2.5 were investigated by analyzing OC and EC characteristics, ratio, and the principal component analysis statistical model. The results showed that the proportions of OC in PM10 and PM2.5 at the various dust fall sites differed, ranging from 6.0% to 19.4% and 7.6% to 29.8%, respectively. The ratios of EC in PM10 and PM2.5at the different dust fall sites were relatively small, accounting for 0.6%-2.2% and 0.2%-3.6% in urban sites, respectively; however, EC was almost undetectable in most peripheral soil dust. The proportions of carbonaceous components in PM10 and PM2.5 followed the order of urban road dust fall>external control dust>river beach soil dust>soil dust and urban road dust fall>soil dust>external control dust>river beach soil dust, respectively. OC dominated the carbonaceous aerosols at the different sites, which was relatively low in urban road dust fall. The OC to total carbon (TC) ratios in PM10 and PM2.5 at urban road dust fall were 85.2%-95.3% and 87.9%-98.9%, respectively. The OC to TC ratios in PM10 and PM2.5 of soil dust were relatively high, exceeding 99%. Carbonaceous components were primarily concentrated in fine particles. The pollution distribution of carbonaceous components in the urban road dust fall sites was consistent, whereas that in the different soil dust sites were quite different. The carbonaceous components in urban road dust fall and soil dust were primarily affected by pollutant source emissions such as biomass burning, coal burning, gasoline, and diesel vehicle exhaust. There were differences in the source contribution rates of carbonaceous aerosols in PM10 and PM2.5.

[Emission Characteristics of Organic Carbon and Elemental Carbon in PM10 and PM2.5 from Vehicle Exhaust and Civil Combustion Fuels].

To study the emission characteristics of carbonaceous aerosol in particulate matter emitted from vehicle exhaust and main civil combustion fuels, organic carbon (OC) and elemental carbon (EC) in PM10 and PM2.5 samples from vehicle sources (gasoline vehicles, light duty diesel vehicles, and heavy duty diesel vehicles), civil coal (chunk coal and briquette coal), and biomass fuels (wheat straw, wood plank, and grape branches) were collected and analyzed by using a multifunctional portable dilution channel sampler and the Model 5L-NDIR OC/EC analyzer. The results showed that there were significant differences in the proportion of carbonaceous aerosols in PM10 and PM2.5from different emission sources. The proportions of total carbon (TC) in PM10 and PM2.5 of different emission sources were 40.8%-68.5% and 30.5%-70.9%, respectively, and the OC/EC were 1.49-31.56 and 1.90-87.57, respectively. The carbon components produced by different emission sources were dominated by OC, and the OC/TC values in PM10 and PM2.5 were 56.3%-97.0% and 65.0%-98.7%, respectively. The proportions of OC in carbonaceous aerosols in PM10and PM2.5 were in the descending order of:briquette coal>chunk coal>gasoline vehicle>wood plank>wheat straw>light duty diesel vehicle>heavy duty diesel vehicle and briquette coal>gasoline car>grape branches>chunk coal>light duty diesel vehicle>heavy duty diesel vehicle, respectively. The main components of carbonaceous aerosols in PM10 and PM2.5 emitted from the various emission sources were different, and source apportionment of carbonaceous aerosols could be accurately distinguished by their ingredient composition profiles.

[Chemical Reaction Activity and Source Apportionment of Atmospheric VOCs in Summer in Dalian].

To investigate the characteristics and source apportionment of atmospheric volatile organic compounds (VOCs) in Dalian, the concentration level, composition characteristics, reaction activity, and source apportionment of atmospheric VOCs in Dalian were analyzed based on high-resolution online observation VOCs data from June to August 2020. The results showed that the average φ(VOCs) was (10.21±5.71)×10-9, in which alkanes accounted for 66.35%, alkenes for 11.89%, alkynes for 7.75%, and aromatics for 14.01%. VOCs and NOx were high at night and low during the day, whereas the change trend of O3 was opposite. Considering the species activity, it was determined that toluene, ethylene, m/p-xylene, 1-hexene, n-butane, isopentane, n-pentane, and isoprene were the key species affecting atmospheric VOCs in Dalian. Priority control of olefin and aromatic hydrocarbon emissions is the key to improve O3 pollution in summer in Dalian. By applying the positive matrix factorization (PMF) model, six major VOCs sources were extracted, namely traffic sources (26.38%), combustion sources (22.75%), industrial emission sources (17.09%), solvent usage sources (14.59%), natural sources (11.72%), and others (7.47%). The emissions of traffic sources and combustion sources are the key pollution sources for O3 prevention and control in Dalian in summer.

[Spectral Characteristics and Source Analysis of WSOC of PM2.5 in Winter of Xi'an].

The spectral characteristics and sources of water-soluble organic compounds (WSOC) in PM2.5 in winter were studied by using UV-vis absorption spectroscopy, three-dimensional fluorescence spectroscopy, parallel factor analysis, and backward trajectory model. The results showed that the concentration of WSOC in PM2.5 was 4.66-14.75 µg ·m-3. The values of E2/E3, E3/E4, S275-295, SUVA254, AAE, and MAE365 of WSOC were, respectively, in the range of 2.85-4.32, 2.21-3.56, 0.0099-0.0127 nm-1, 2.35-3.89 m2 ·g-1, 2.66-4.60, and 1.51-2.60 m2 ·g-1. The E2/E3, E3/E4, S275-295, and AAE values of WSOC at the sampling site in the southern suburb of Xi'an, China (Xi'an University of Architecture and Technology) were higher than those at the sampling site in the northern suburb (sports park), while the values of SUVA254 and MAE365 were lower. There were four fluorescent components in WSOC identified by the EEMs-PARAFAC model: C1 and C2 were fulvic acid-like and protein-like, respectively, and C3 and C4 were humus-like components. The fluorescence intensities and the sum of the fluorescent components were positively correlated with the concentrations of PM2.5, OC, WSOC, and A254 value (P<0.01). The fluorescence index (FI), biological source index (BIX), and humic index (HIX) values of WSOC were 1.75-2.12, 1.14-1.46, and 1.18-2.06, respectively. During the monitoring period, the air mass transmission trajectory was dominated by the local southwest of short-distance transmission, and its trajectory accounted for more than 50%. The pollutant emissions from Xinjiang, Inner Mongolia, and Gansu also made significant contributions to the air pollution levels in Xi'an in winter. There was a small difference in the carbon component content of PM2.5 in the northern and southern suburbs of Xi'an. The molecular weight, humification degree, and light absorption capacity of WSOC at the southern suburb sampling site were lower than those in the northern suburb where the wavelength dependence of light absorption intensity was relatively stronger. The WSOC mainly originated from biological sources or both from biological and terrestrial sources. Local transmission had the most significant contribution to PM2.5 and WSOC in winter.

[Fluorescence Characteristics and Source Analysis of DOM in Snowfall of Xi'an].

Fluorescence characteristics and sources of dissolved organic matter (DOM) in snowfall in Xi'an were studied by three-dimensional fluorescence spectroscopy, parallel factor analysis, and backward trajectory model, which provided a data basis for the analysis of the chemical composition and source of atmospheric organic pollutants. Results show that the DOC content of DOM was 0.88-10.92 mg·L-1. DOM mainly contained humus-like, fulvic acid-like, tryptophan-like, and tyrosine-like substances. The fluorescence intensity and the summed intensities of these substances exhibited significant positive correlations with the DOC and UV254 (P<0.01). The fluorescence index (FI), biological source index (BIX), and humic index (HIX) values of DOM during snowfall were 1.50-1.75, 0.87-1.25, and 1.11-1.97, respectively. FI was positively correlated with BIX and negatively correlated with HIX (P<0.05). During snowfall, the air mass transmission trajectories included the local transmission, long-distance transmission starting from Xinjiang (through Gansu and Ningxia), and medium-distance transmissions starting from Inner Mongolia (through Ningxia) and Shandong (via Henan), accounting for 38.78%, 24.04%, 19.87%, and 17.31% of the total, respectively. This indicates that the content or relative content of the DOM contained in the precipitation can be characterized by fluorescence intensities and their sums of the humic-like, fulvic acid-like, tryptophan-like, and tyrosine-like tyrosine. The DOM in snowfall had both biological and terrestrial characteristics, and belonged to a self-generated source with the newly produced organic matter or matter with stronger self-source characteristics. Local transmission had the most significant contribution to the source of snowfall DOM.

[Analysis of Pollution Characteristics and Sources of PM2.5 During Heavy Pollution in Shijiazhuang City Around New Year's Day 2019].

We report on successive haze weather that occurred in Shijiazhuang City, China, from December 30, 2018 to January 15, 2019. There were 12 days of heavy atmospheric pollution during this period, which primarily involved aerosol fine particulate matter (PM2.5). This study analyzes the causes of the pollution using component analysis and by assessing pollution evolution, spatial and temporal distributions of PM2.5, pollution sources, and meteorological factors. The results showed that PM2.5 was mainly composed of secondary inorganic ions (65.4%) that were mainly sourced from coal combustion (24.4%) and industrial sources (23.7%). The contributions of sulfate and secondary inorganic sources increased significantly with increasing pollution. Pollution was affected by unfavorable meteorological conditions (e.g., a low air mass) and by the particular local terrain, static stability, high humidity, and near-ground reverse temperatures from the south-southeast and west-southwest directions. Contaminants from primary sources including coal combustion, industry, and motor vehicle exhausts accumulated quickly in front of the Taihang Mountains. Secondary transformation of gaseous pollutants and increasing moisture absorption of particulate matter increased PM2.5 concentrations. Sulfate explosion also increased pollution. We recommend that as part of emergency responses to heavy pollution events, emissions reduction measures should be implemented to strengthen the control of SO2, NOx, and NH3 emission sources of secondary inorganic precursors, especially SO2 emission sources (i.e., coal etc.). We further propose a strengthen of the management of atmospheric emission sources in Xinle, Wuji, Shenze, Jinzhou, and Xingtang counties in the northeast of the city to reduce the impact of local transmission.

[Pollution Characteristics and Sources of Carbonaceous Components in PM2.5 in the Guanzhong Area].

In order to study the pollution characteristics and sources of fine particulate matter in the Guanzhong area of China, PM2.5 samples were collected and observed by hand from September 4, 2017 to January 19, 2018 at five sites (XA, WN, TCH, BJ and XY). The carbonaceous component of these samples was analyzed by thermal-optical transmission, which showed that the average concentrations of OC and EC in the fine particulate matter were (14.48±7.86) µg·m-3 and (2.27±0.95) µg·m-3, respectively, Percentages of OC and EC were 18.04% and 2.99%, respectively. Compared with other cities, the measured levels of pollution in the Guanzhong areas were more severe. The spatial distribution of percentage of carbon component in PM2.5 was XY > WN > XA > BJ > TCH, and the concentrations in winter were higher than in autumn. The correlation between OC and EC was significant (R2=0.79), which indicates a common source. The highest proportion of OC1 was 23.44%. The concentration of the carbonaceous component from high to low was OC1 > EC2 > EC3 > OC4 > EC1 > OC2 > OC3 > EC4 > EC6 > EC5. The results of PMF modeling show that the four main contributing sources of carbon components in pollution in this area are biomass combustion and coal-burning, gasoline vehicle exhaust emissions, diesel vehicle exhaust emissions, and road dust, contribution 48.63%, 23.07%, 18.82%, and 9.47%, respectively. Furthermore, there were clear differences in the pollution structure at each study site.